جستجوی مقالات مرتبط با کلیدواژه "meandering channel" در نشریات گروه "آب و خاک"

Generally, due to the presence secondary flows in the curvature of the river, the outer wall in the bend is always subjected to degradation and erosion. These streams divert the surface flow lines towards the outer wall and the flow lines close to the substrate to the inner wall. Therefore, studying the flow in the meandering channels in order to prevent erosion is of particular importance. One of the simplest, yet most economic methods to cope with outer wall erosion is the use of spur dike. For this purpose, in this laboratory study, the effect of the presence and absence of series spur dikes on longitudinal velocity components in a channel meandering with sloped erodible wall is investigated. The results showed that the presence of simple series spur dikes cause reduced the flow velocity in the outer wall of the bend. Therefore, the average highest velocity reduction between the second and third spur dikes and the lowest velocity reduction between the third and fourth spur dikes was performed. Also, the studies showed that with the increase of 33% of the discharge, about 5% were added to the performance of the spur dikes in reducing the flow velocity in the outer wall of bend.

Spur dikes as one of the main structures in river restoration practices are used for protecting and shaping the river banks and main channels. These structures growing from the river natural banks, having suitable length and angle relative to the flow direction and cause deviation of the flow from the riversides and driving it to the central axis of the river. In this study, the numerical hydrodynamic and sediment transport model “CCHE2D” was used to simulate the flow pattern and streambed changes around the spur dikes. Two separate series of experimental data were used to assess the numerical model outputs. The accuracy of the model outputs were evaluated through common statistical parameters including RMSE, MARE, REmax and R2. Comparison of the experimental results with the simulated values revealed that the CCHE2D was reasonably capable to simulate the flow pattern around the both of single and series of spur dikes with high accuracy (correlation coefficient=0.755-0.955). The bed changes around the series of spur dikes were simulated with acceptable accuracy, revealed that the CCHE2D model could precisely predict the maximum scouring depth with correlation coefficient of 0.990, but overestimated the width of scour hole around the spur dike in comparison with experimental observations. Furthermore, both the numerical results and experimental observations showed that the erosion depth of main channel had a direct relation with the length of spur dike.